A level chemistry group 7
- Created by: _georgia.wilson_
- Created on: 24-06-20 00:10
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- Group 7
- Halides
- Reducing agent: reducing power increases due to e_ distance + shielding increasing so weaker attraction makes it easier to lose an e-
- Sulfuric acid: all halides react with conc H2SO4 to give a HX to begin with. Some halides can reduce further
- NaF/NaCl: Produces NaHSO4(s) + HCL/HF(g) misty fumes
- NaBr: first reaction is the same but the HBr reduces sulfuric acid: 2HBr(aq) + H2SO4(l) => Br2(g) + SO2(g) + 2H2O(l) chocking fumes of SO2 and orange fumes of Br2
- NaI: same 1st reaction, same 2nd reaction (produces grey I2(s)+purple gas
- HI reduces the SO2 to H2S (bad egg smell) 6HI(g) + SO2(g) => H2S(g) + 3I2(s) + 2H2O(l)
- Testing for halides: add dilute nitric acid then silver nitrate solution to form a precipitate Ag+(aq) + X-(aq) => AgX(s) chloride: white bromide: cream iodide: yellow
- add ammonia solution(NH3,aq,) Cl- dissolves in dilute NH3, Br- dissolves in conc NH3, I- insoluble in conc NH3
- Halogens
- Properties down the group: boiling point increases due to Van der Waals forces electronegativity decreases.....shielding+e- distance colour gets darker less reactive
- Displacement: halogens are oxidising agents, less oxidising down group a halogen will displace a halide that's below it in the periodic table
- chlorine will displace bromide (orange solution) and iodide (brown solution) bromine will displace iodide(brown solution)
- chlorine
- Disproportion when Cl2 reacts with H2O to produce 2H*+(aq), Cl*-(aq), 1/2O2(g)
- Sunlight > decompose to form chloride ions and O2
- Disproportion of Cl2 (reduced and oxidised) to produce bleach,NaCl22NaOH(aq) +Cl2(g) => NaClO(aq) + NaCl(aq) + H2O(l)
- chlorate(I) ions kill bacteria ( in ClO), so can be added to water to make it safe in low concentration
- Disproportion when Cl2 reacts with H2O to produce 2H*+(aq), Cl*-(aq), 1/2O2(g)
- Halides
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